Moxxi's Endowment

root@eridian-db:~$ cat description.txt

A unique Eridian relic that increases combat experience gained from enemy kills, making it a leveling tool rather than a combat relic. Its value drops once leveling speed matters less than the combat bonuses you give up in the relic slot.

root@hyperion-db:~$ cat notes.txt

It is awarded for completing The Good, the Bad, and the Mordecai. The experience bonus increases with the relic's level, so later versions are stronger but still compete with more powerful combat relics.